file pointer shift

I had a code that did reverse each line of the file in a single-byte encoding. Now it took to do this for UTF-8. Rewrote under wide char (code below). It also reverses strings, but some characters are lost. I understand that the problem is with the fseek functions at the end of the loop body. But I can not solve it myself.

#define NULL_TERMINATOR '\0' #define NEW_LINE '\n' int main() { size_t i = 0; file = _wfopen(L"rev.txt", L"r+, ccs=UTF-8"); wchar_t b[4096]{ NULL_TERMINATOR }; while ((fgetws(b, sizeof(b), file)) != NULL) { if (b[wcslen(b) - 1] == NEW_LINE) { b[wcslen(b) - 1] = NULL_TERMINATOR; wcsrev(b); b[wcslen(b)] = NEW_LINE; } else wcsrev(b); fseek(file, i, SEEK_SET); int t=fwrite(b, wcslen(b)*2, count, file); i += wcslen(b)*2+3; fseek(file, i, SEEK_SET); } return 0; }